One of electrophotographic image forming apparatuses comprises, for example, an LED head having a plurality of LEDs (light emitting elements) arranged in a row, and forms an electrostatic latent image by exposing a photoreceptor line by line by this LED head. A color image forming apparatus comprises a plurality of above-mentioned LED heads corresponding to each color, and forms an electrostatic latent image by each LED head, so that a color image is ultimately formed on a body to be transferred, with each color image developed from respective electrostatic latent images overlapped one after another.
Here, it is ideal for an LED head to comprise LEDs all aligned in a straight line. However, such an LED head is difficult to manufacture, and thus, in an actual LED head, a part of LEDs is distributed out of a straight line. Moreover, this arrangement distribution of LEDs is different for each LED head. Consequently, the above image forming apparatus may produce a different shape of exposing line for each LED head corresponding to each color, and, as a result, a color image having a positional deviation (color deviation) between each color image is formed on a body to be transferred, thereby causing degradation of image quality.
One proposed solution includes an image forming apparatus that is capable of conducting correction processing for restraining degradation of image quality caused by the difference of arrangement distribution of LEDs. In particular, an arrangement deviation amount of each LED in a sub-scanning direction is recorded in a memory as correction data, and a timing of light emission of each LED is adjusted so as to offset the above-mentioned arrangement deviation amount based on the correction data, thereby allowing an exposure pattern to become closer to an ideal straight line.